Dual element fuse device



May 2, 1961 w. H. EDMUNDS DUAL ELEMENT FUSE DEVICE 2 Sheets-Sheet 1 Filed Dec. 27, 1957 INV ENTOR.

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May 2, 1961 w. H. EDMUNDS 2,982,834

DUAL ELEMENT EusE DEVICE 2 Sheets-Sheet 2 Filed Dec. 27, 1957 United States Patent O DUAL ELEMENT FUSE DEVICE William Harold Edmunds, Havertown, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia, Pa., a corporation of Pennsylvania Filed Dec. 27, 1957, Ser. No. 705,625

8 Claims. (Cl. 200-1`16) My invention rel-ates to a fuse device having both a fusible element and an overload element therein where the overload element may operate latch means within the fuse device responsive to predetermined overloads.

Presently available fuse devices are constructed to serve for both short circuit and overload protection and are unable to select between the two.

It is `apparent that once the fuse operates due to an overload it must be replaced by a new fuse. Furthermore, it is substantial-ly impossible to calibrate a fuse for overload conditions other than by physical dimensions of the fusible element. That is -to say, if the overload capacity of a fuse is measured by passing overload electrical currents through it, the fuse will be operated and destroyed.

The primary object of my invention is to provide a novel dual element fuse device wherein a fusible element serves to operate on high short circuits, while an auxiliary overload device is contained within the same fuse housing and is responsive to heat developed in the fusible member to operate a latch means which eventually serves to operate a series connected contact device.

In a preferred embodiment of my invention a fusible link and a birnetal actuated latch member are contained within a single fuse housing. The bimetal actuated latch device is positioned with respect to the current carrying fusible member so as to be deflected in accordance with the current passing through the fusible member. One of the members of the latch device is then connected to a spring biased plunger which is normally held in an inoperative position.

When, however, the cur-rent through the fusible member is of overload magnitude insucient to cause operation of the fusible member and iiows for a predetermined length of time, the bimetal portion of the latch will sufficiently deiect to release the latch member holding the spring biased plunger in position. The spring biased plunger is then released and may cause actuation of a series connected contacting `device such as a circuit breaker so as to cause interruption of the overload.

Details of the interaction between a fuse having a plunger associated therewith `and a circuit breaker are fully set forth in my copending applications, Serial Nos. 461,378 and 472,969, now Patent No. 2,888,535, filed October ll, 1954, and December 3, 1954, entitled Circuit Breaker Having Electrical and Mechanical Co-ordination with a Current Limiting Device and Removable and Replaceable Current Limiter Housing for Circuit Breakers, both to William Harold Edmunds, respectively, and assigned -to the assignee of the instant invention.

With the above type system, it is seen that the fuse f. ICC

device need not be replaced after an overload operation, as would be true of presently available fuse devices. Conversely, it is only necessary now to reset the overload latch member and series connected circuit interrupter to reconnect the circuit.

My novel dual element fuse may be further adapted with magnetic tripping means by positioning a relatively movable magnetic member on the bimetal element arm and causing that portion of the bimetal arm to conduct at least a portion of the fuse current. A second and stationary magnetic structure is then positioned adjacent the movable magnetic structure so that, responsive to a rapid increase in the current through the fuse as in a relatively low short circuit current condition, the magnetic eld generated by the current carrying portion of the bimetal would be suicient to cause the relatively movable magnetic member to be drawn towards the relatively stationary member and thus defeat the latching device to cause operation of the plunger and subsequent operation of the series connected interrupting device.

In this case there are three distinct types of interruption possible. The first is the above described low short circuit current interruption; and second is overload current interruption due to thermal deflection of the bimetal. In each of these two cases the fuse plunger is released to thereby cause operation of a series connected contact interrupter.

The third type of interruption occuts on extremely high short circuit currents and is achieved by the fusible element of the fuse. In some types of fuses, the fusible element will also operate on a short circuit current having a greater rise which is beyond a predetermined value. In this case, the fusible element of the fuse itself, which may be constructed as set forth in U.S. Patent No. 2,592,399 to W. S. Edsall et al., will interrupt the short circuit current which may be too severe to be interrupted by the series connected contacting device, thus permitting the use of a relatively low capacity circuit interrupter (for only loverload and relatively low short circuit current iuterruption) in a high capacity circuit.

It is to be noted that my novel invention may be applied to three-phase systems where each phase is provided with one of my novel fuses and an associated contacting device. The contacting devices may each be operated from a common trip member which is in turn operated by any of the three fuse devices. Accordingly, when any fuse device is operated its plunger is ejected, the common tripper bar of the circuit interrupting device is operated and each of the contacts in each of the phases is opened to thereby prevent single phasing.

Accordingly, another object of my invention is to provide a novel compact fuse for initiating overload operation without necessitating fusereplacement.

Another object of my invention is to provide a novel fuse which can be calibrated for overload operation without destroying the fusible element.

Another object of my invention is to provide a novel multiple unit fuse wherein either overload or relatively low short circuit currents will initiate the operation of a mechanically interlocked contact device.

A still further object of my invention is to provide a novel fuse Iwhich is not destroyed on either overload operation, or low short circuit current operation.

These and other Vobjects of my invention will become 3 apparent from the following description when taken in conjunction with the -drawings in which:

Figure 1 is an exploded perspective View of one embodiment of my novel invention.

Figure 2 is a `side cross-sectional view of the embodiment of Figure 1.

Figure 3 is a side cross-sectional view of a second ernbodiment of my novel invention.

Figure 4 is `a cross-sectional view of Figure 3 when taken across the lines 4-4.

Figure 5 is a cross-sectional view taken throughone phase ott a multi-phase unit wherein my novel fuse dedevice is mechanically interlocked with a circuit breaker.

Referring now to Figures 1 and 2 lwhich show a iirst embodiment of my invention, a fuse housing is formed of a cylinder 20 of insulating material, the top and bottom of which is sealed by conductive disk members 22 and 24- respectively. These conductive disk members 2l2 and '24 are sealed within the body 20 of insulating material any desired manner and form a relatively airtight space within the housing assembly. i The outsides `of each of the conductive members 22 and 24 are adapted to serve as connectors to la circuit which is to be lprotected by the device, the connection being made in any desired manner, as "by insertion in a spring clip device.

However, it will be obvious to anyone skilled in the art that the outer surfaces of members 212 and 24 may be adapted in any desired manner to form terminal connection means. By way of example, the disk conductors may be adapted with tulip clip type connectors as shown in U.S. Patent No. 2,805,294 `entitled Mounting Block `for Circuit Breakers, issued September 3, 1957, to Willim Harold Edmunds, `and assigned to the assignee of the instant application.

A first land second fusible member 26 and 28 respectively are electrically connected from conductive member 22 to conductive member 24 and yare positioned within housing 20, and may be either `simple fusible wires or could be vfusible elements of `the type -set forth in the above noted U.S. Patent No. 2,592,399 to W. S` Edsall et al. It is to Xbe Ifurther noted that two parallel fusible members are shown here for illustrative purposes only, and a single member or `any number of members could be used.

From the above, it is apparent that when'the fuse is connected to -an electrical circuit by means of connectors 22 and 24, the fusible elements V26 and 28 will each be connected in series with that circuit.

A second cylinder 30 which is made of Vheat 1conductive material and is insulated from Athe electrical circuit, as by forming the end of heat conductive cylinder 30 of an insualting gasket 32, is co-axially positioned with respect to insulating housing 20, land is positioned between each of the Vfusible elements 26 and 28. Heat conductive cylinder 30 then has a bimetal or thermal element 34 positioned therein which is supported by conductive disk 22 and is terminated by a iirst llatch member 36.

A second `and cooperating latch member 38 is then supported by member 40 which extends toward a centrally positioned aperture in conductive disk 24 and through the 'aperture to terminate in an enlarged'plungerhead 42.

At least a portion of member 40 is preferably constructed off insulating material to prevent a conductive path through the latch structure. However, there may be instances where this conductive path is desired `as when latch members 36 and 38 serve as cooperating con tacts as well as latch members;

The latch 36 may be made ofan insulating material or insulated from latch 38 if the magnitude of current therethrough would be of suiiicient magnitude to draw detrimental arc across the latch 36-38.

The plunger-head 42 is VVnormally positioned within a recess 44 of disk 24 as :best seen in Figure 2, and is biased outwardlyfbly thebiasing spring 46 which is placed between a seat in recess 44 yand the plungenhead 42. However, plungerdhead 42 is normally maintained within recess 44 `and the spring 46 maintained compressed by the latch engagement between latches 36 and 38. When, however, this latching engagement is defeated and latch member 38 is -f'rce to move independently of latch member 36, spring 46 will be operative to eject plunger 42 to some external position.

In operation of the embodiment set .forth in Figures 1 and 2, it is clear that severe vfault currents will be interrupted by the fusible members 2,6 land 28.

Under these severe short circuit conditions, the bimetal 34 is destroyed so that the fuse combination cannot 'be reset. That is since the -fuse links will rupture under severe short circuit conditions, the bimetal 34 must be designed to 4be destroyed by this -magnitude ofl current to thereby insure that the fuse unit is not reused.

It however, the fault current is of overload dimensions, the fuse elements may be saved by causing plunger 42 to be `operated into mechanical engagement with the trip means of a series connected contacting device.

Thus, when the current through fusible elements 26 and 28 is beyond some predetermined magnitude and ows `for some predetermined time, the heat conducting tube 30 will pass heat to the bimet-al element 34 to cause the bimetal to deiiect upward in Figure 2, :and thus defeat the latch engagement between latch members 36 `and 38. This then allows the plunger 42 to be released, .and the associated contacting device will subsequently interrupt the overload current. y

The latch members 36 and 38 may have adjusting means associated therewith (not shown) which may be of any type well known to the art so that the overload characteristics of the fuse can be accurately controlled.

More speciiically, bimetal 34 has a U-shaped magnetic structure 50 attached thereto, in a second embodiment of this invention (Figures 3 and 4), by screw means '52 and .is positioned to have a relatively stationary armature 54 adjacent thereto and rigidly attached in any desired manner to insulated housing 20.

A conductive path is then formed 'to include conductive 'disk 22, birnetal 34 `and a pigtail 56 which is `connected from latch member 38 to conductive disk24.

Thus, a relatively small portion of the current flowing through the fuse device will flow through bimetal 34 and its respective movable magnetic `structure 50.

Accordingly, the Vfuse device will stil-l operate in the manner heretofore set forth in conjunction withV Figures '1. and 2, but, upon the occurrence of relatively low short clrcuit currents, the current Viiowing through bimetal 34 will generate a strong lenough magnetic eld through U- Shaped magnet 50 to cause it ht0 be attracted to armature 54. Since this will cause the bimetal 34 to deflect in the Vsame manner as would a thermal overload, the latch lengagement between latch members 36'and 38 will be defeated in a similar manner to once again cause ejection of the plunger 42.

Figure 5 'shows the manner in which the multielement fuse of Figures 3 and 4 may be associated with a circuit interrupting device. More specifically, Figure 5 is a cross-sectional View through one phase of acircuit interrupter of the type shown in my copending application, Serial No. 622,042, iiled November 14, 1956, entitled End Mounting of a Current Limiting Device Associated with a Circuit Breaker, to William Harold Edmunds, and assigned to the assignee of the instant invention, with the circuit breaker thermal and magnet-ic trip units removed, andthe novel current limiting fuse including these elements,

In Figure 5, my novel fuse device of Figures 3 and 4 isseen generally at numeral'i), 4and it is seen that the disk connectors 22 and 2'4- respectively are'adapted with terminal connectors 62 and 64 respectively, which cooperate with tulip clip type connectors 466 and 68 -re` spectively, supported by a circuit breaker base.

f The combination of the circuit breaker and my novel fuse may then be connected into a circuit by means of tulip clip connectors 70 and 72 respectively, which cooperate with terminals 74 and 76 respectively of energizable current conductors 78 and 80 respectively.

The connection of my novel fuse device 60 then completes a current path between current conductors 78 and 80, which includes terminal 70, terminal 66, terminal 62, fuse device 60, terminal 64, terminal 68, conductor 82, current connecting means (not shown) from conductor 82 to movable contact 84, stationary contact 86, terminal 72, terminal 76 and thence to current conductor 80.

With regard to the circuit breaker mechanism, it is seen that the circuit breaker includes cooperable contacts 84 and 86 which are connected in series with my novel fuse device.

It is to be understood, as is more completely described in my copending application, Serial No. 622,042, led November 14, 1956, that Figure shows only a single phase of what could be a multi-phase unit. Thus, each of the phases would include a pair of cooperable contacts similar to contacts 84 and 86 which are connected in series witha respective fuse device such as fuse 60.

Each of the pairs of cooperable contacts are then provided with an operating mechanism seen generally at 88 which may be operated from external operating handle 90. This operating mechanism may be of any type well known to the art, and for purposes of illustration, could be of the type shown in my U.S. Patent No. 2,574,093 issued November 6, 195,1, entitled Adjustable Trip, to W. H. Edmunds, and assigned to the assignee of lthe instant invention.

When the circuit breaker cooperating contacts 84 and 86A have been moved to their engaged position, a latch member, such as latch member 92, engages a cooperating latch 94 which is supported by rotatable tripper bar member 96. So long as this latch engagement is maintained, biasing means which tend to move the cooperating contacts to a disengaged position are defeated.

Thus, in order to automatically cause circuit breaker contact engagement, it is necessary to rotate tripper bar 96 in a counter-clockwise direction, thereby releasing the latch engagement between members 92 and 94. It is to be noted that tripper bar 96 is common to each phase of the circuit breaker, so that rotation thereof due to the mechanism associated with any phase of the circuit breaker will cause disengagement of contacts in each phase of the circuit breaker.

In accordance with the instant invention, this trip means for operating the circuit breaker contacts will be operated responsive to movement of plunger 42 of Figure 3 through the mechanism by which my novel fuse device is mechanically interlocked with the circuit breaker. This mechanism may be of any type, and the mechanism described hereinafter is for illustrative purposes only.

Thus, by way of example, the fuse device 60, which is shown as being mounted Within a housing 98 which is removably connected to the circuit breaker housing, is further associated with an auxiliary tripper bar 100 which is pivotally mounted on the same housing, and has extending arms 102 and 104. Arms 102 and 104 are continuous members with the end of arm 104 being forced into engagement with the left-hand end of member 106 by means of a biasing spring 108 which is positioned at the top of member 102 and biases members 102 and 104 in a counterclockwise direction.

Member 106 is positioned to be axially movable and contains a notch 110 which cooperates with an extension 112 fastened to the tripper bar 96.

A spring 114 biases member 106 to the left so that the right-hand end of notch 110 presses against member 112 to thereby bias tripper bar 96 in a counterclockwise direction.

Arm 102 of vauxiliary tripper bar 100 is further positioned to be yadjacent and operatively connectible to plunger 42 of my novel fuse device when this plunger is ejected due to defeat of the latch engagement between latch members 36 and 38 in Figure 3.

Thus, responsive to either an overload or a relatively low short circuit current, plunger 42 is ejected, as described in conjunction with Figure 3, and is brought into engagement with arm 102 so as to force arm 102 to rotate in a clockwise direction against the force of biasing spring 108.

This then causes arm 104 to rotate in a counterclockwise direction and allows the member 106 to be moved to the left by its biasing spring 1114, thereby driving member 112 and tripper bar 96 in a counterclockwise direction to achieve tripping of the circuit breaker contacts 84 and 86.

It is to be noted that if the fuse housing 98 is physically disconnected from the circuit breaker housing, arm 104 will be removed from the left-hand end of member 106 so that tripper bar 96 may once again be operated to disengage the circuit breaker contacts and thus achieve positive disconnection of the circuit connected to the circuit interrupting device.

Once the circuit interrupting device has been operated and latch members 36 and 38 of Figure 3 have disengaged due to overload or low short circuit circuit fault currents, the fuse may be easily re-set by merely forcing plunger 42 of Figure 3 to the left and against the force of biasing spring `46.

In the embodiment of Figure 5 it is clear that reset of the fuse device can be easily achieved by mechanical means (not shown) which will engage plunger 42 and move the plunger to the left responsive to movement of operating handle to a reset position.

In the foregoing, I have described my invention only in connection with preferred embodiments thereof. Many variations and modifications of the principles of my invention within the scope of the description herein are obvious. Accordingly, I prefer to be bound not by the specic disclosure herein but only by the appending claims.

What is claimed is:

l. A dual element fuse comprising a housing containlng a fusible element and an independent overload responsive element, said overload responsive element being operative responsive .to the passage of a predetermined current through said fuse for a predetermined time, said current being insuflicient to operate said fusible element; said overload responsive element including a normally latched latch means and a bimetal element; said bimetal element being deflected responsive to flow of said predetermined current; said bimetal being positioned to be operatively connected to said latch means responsive to said deflection to defeat said normally latched latch means; said overload responsive element being positioned within a heat conductive member constructed to conduct heat generated by said fuse element to said bimetal element.

2. A fuse device comprising a housing containing a fusible element, a thermal `trip element and a magnetic trip element; said thermal trip element comprising a bimetal element operatively connected to latch means; said magnetic trip element comprising a movable magnetic member carried by a portion of said bimetal and positioned adjacent a relatively stationary magnetic member; said portion of said bimetal carrying said movable magnetic member having circuit connections made thereto for carrying at least a portion of said fuse current to generate a magnetic tield coupling said movable magnetic member and said relatively stationary member to exert a force on said bimetal tending to operate said latch means; said bimetal operating said latch means responsive to either a predetermined increase of the temperature of said bimetal or to a relatively low short circuit current through said Ycurrent conducting portion of said bimetal;

said fusible element being operated responsive to a relatively high short Vcircuit current through said fuse; said thermal trip element being operatively positioned with respect to said fusible element whereby the former is subjected to heat generated by the passage of current through the latter; said'thermal trip element being positioned Within a heat conductive member constructed to conduct heat generated by said fusible element to said thermal trip element.

3. A mechanically interlocked fuse and circuit breaker combination, said fuse an'd circuit breaker being electrically connected in series, said fuse member having mechanically movable means associated therewith normally latched against movement byrlatch means, said circuit breaker having trip means associated with the contacts of said circuit breaker' for tripping said circuit breaker responsive to operation thereof, said circuit breaker trip means being operatively connectable to said mechanically movablev means responsive to operation of said latch means to permit movement of said mechanically movable means; said fuse comprising a dual element fuse having a fusible element and an overload responsive element, said overload responsive element being operatively connected to said latch means to operate said latch means responsive to predetermined overload conditions; said overload responsive element comprising a bimetal element exposed to temperature variation due to current flow through said fusible element; said bimetal element being electrically insulated from said fusible element.

4. A mechanically interlocked fuse and circuit breaker combination, said fuse and circuit breaker being electrically connected in series, said fuse member having mechanically movable means associated therewith normally latched against movement by latch means, said circuit breaker having trip means associated with the contacts of said circuit breaker for tripping said circuit breaker responsive to operation thereof, said circuit breaker trip means being operatively connectable to said mechanically movable means responsive Vto operation of said latch means to permit movement of said mechanically movable means; said latch means being normally latched; said fuse comprising a dual element fuse having a fusible element and an overload responsive element, said overload responsive element comprising a bimetal element exposed to temperature variations due to current flow through said fusible element; said bimetal element being deflected responsive to flow of said predetermined current; said bimetal being positioned to be operatively connected to said latch means responsive to said deection to defeat said normally latched latch means; said bimetal element being Voperatively positioned with respect to said fusible element whereby the former is subjected to heat generated by the passage of current through the latter; said bimetal element being electricallyV insulated from said fusible element.

5. A mechanically interlocked fuse and circuit breaker combination, said fuse and circuit breaker being electrically connected in series, said fuse member having mechanically movable means associated therewith normally latched against movement by latch means, said circuit breaker having trip means associated with the contacts of said circuit breaker for tripping said circuit breaker responsive to operation thereof, said circuit breaker trip means being operatiyely'connectable to said mechanically movable means responsive to operation of said latch means to permit movement of said mechanically movable means; said fuse comprising a dual element fuse having a fusible element and an overload responsive element, said overload responsive `element being operatively connected to said latch means to operate Said latch means responsive to predetermined overload conditions; said overload responsive element 'comprising a bimetal element exposed to temperature Vvariation Vdue to current flow through said fusible element; said overload responsive element being positioned within a' heat conductive member constructed `to conduct heat generated by said fuse element to said bimetal element.

6. A mechanically interlocked fuse and circuit breaker combination, saidV fuse and circuit breaker being electrically connected in series, said fuse member having mechanically movable means associated therewith normally latched against movement by latch means, said circuit breaker having trip means associated with the contacts of said circuit breaker for tripping said circuit breaker responsive to operation thereof, said circuit breaker trip means being operatively connectable to said mechanically movable means responsive to operation of said latch means to permit movement of said mechanically movable means; said fuse comprising a dual element fuse having a fusible element and an overload responsive element, said overload responsive element being operatively connected to said latch means to operate said latch means responsive to predetermined overload conditions; said overload responsive element comprising a bimetal element exposed to temperature variation due to current flow through said fusible element; at least a portion o f said bimetal element being electrically connected in parallel with said fusible element; said Vbimetal element being electrically insulated from said fusible element.

7. A mechanically interlocked fuse and circuit breaker combination, said fuse and circuit breaker being electrically connected in series, said fuse member having mechanically movable means associated therewith normally latched against movement by latch means, Vsaid circuit breaker having trip means `associated With the contacts of said circuit breaker for tripping said circuit breaker responsive to operation thereof, said circuit breaker trip means being operatively connectable to said mechanically movable means responsive .to operation of said latch means to permit movement of said mechanically movable means; said fuse device comprising a housing containing a fusible element, a thermal trip element and a magnetic trip element; said thermal trip element comprising a bimetal element operatively connected to said latch means; said magnetic trip element comprising a movable magnetic member carried by a portion of said bimetal and positioned adjacent a relatively stationary magnetic member; said portion of said bimetal carrying said movable magnetic member having circuit connections made thereto for carrying at least aY portion of said fuse current to generate a magnetic field coupling said movable magnetic member and said relatively stationary member to exert a force on said bimetal tending to operate said latch means; said bimetal operating said latch means responsive to either a predetermined increase of the temperature of said bimetal or to a relatively low short circuit current through said current conducting portion of said bimetal` 8. A mechanically interlocked fuse and circuit breaker combination, said fuse and circuit breaker being electrically connected in series, said fuse member having mechanically movable means associated therewith normally latched against movement by latch means, said circuit breaker having trip means associated with the contacts of said circuit breaker for tripping said circuit breaker responsive to operation thereof, said circuit breaker trip means being operatively connectable to said mechanically movable means responsive to operation of said latch means to permit movement of said mechanically movable means; said fuse device comprising a housing containing a fusible element, a thermal trip element and a magnetic trip element; said thermal trip element comprising a bimetal element operatively connected to said latch means; said magnetic trip element comprising a movable magnetic member carried by a portion of said bimetal and positioned adjacent a relatively stationary magnetic member; said Aportionof Saidtbimetal carrying said movable magnetic member having circuit connections made thereto for carrying at least a portion of said fuse current to generate a magnetic field coupling said movable magnetic member and said relatively stationary member to exert a force on said bimetal tending to operate said latch means; said bimetal operating said latch means responsive to either a predetermined increase of the temperature of said bimetai or to a relatively low short circuit current through said current conducting portion of said bimetal; said fusible element being operated responsive to a relatively high short circuit current through said fuse.

References Cited in the file of this patent UNITED STATES PATENTS 

